Computational modeling of meandering channel evolution and width adjustment

Meandering channel migration, as a result of bank erosion, attracts substantial attention from engineers and scientists since the retreat of bank lines can seriously affect floodplain dwellers, damage riparian vegetation, and endanger bridge crossings and bank-protection structures (ASCE TC, 1998). Eroded, fine-grained bank material may pose a hazard to aquatic habitats and contribute to sedimentation problems downstream (Darby and Thorne , 1994).; Extensive research on the migration of meandering channels has been conduct in the past. However, this is a complex morpho-dynamic process resulting from interactions among flow, sediment, and movable boundaries. The migration of meandering channels is not completely understood, and modeling meandering channel migration is still a challenging problem in the area of river engineering.; In this dissertation, the bank erosion model of Duan et al. (2001) is modified and applied to simulate experimental and natural processes of width adjustment and meandering channel evolution. In the modified model, the rate of bank erosion is a resultant of basal erosion and bank collapse. Basal erosion, including lateral erosion and near-bank bed degradation, is calculated as a gradient function of the longitudinal sediment transport rate and strength of the secondary flow rather than being proportional to the excessive near-bank velocity or shear stress. Additionally, bank height, side slope, and thickness of each layer in the vertical structure of the bank are taken into consideration in the modified model.; An analytical model intended to simulate the evolution of a meandering channel centerline is developed based on the analytical solution of flow field in a sine-generated meandering channel and implementation of the modified bank erosion model. Evolution of meandering channels from mildly- to highly-sinuous channels is replicated with this model. Simulation results show the migration of meandering channels is a combination of downstream translation, lateral extension, expansion, and downstream and upstream rotation. (Abstract shortened by UMI.)...